1. Field of the Invention
This invention relates to a fire alarm system, and more particularly to a fire alarm system, to which terminal units, such as fire detectors, manual boxes and transmitters (transmitters for supervising fire detectors and manual boxes or transmitters for controlling local sound units, fire block doors, smoke blocking and exhausting units and fire extinguishing units) are connected.
2. Description of the Related Art
Hitherto, there has been a fire alarm system, such as a fire alarm system, in which a multiplicity of terminal units, such as transmitters to which one or more types of controlled units, such as fire detectors and manual boxes or fire detectors, local sound units and smoke blocking and exhausting units are connected, are installed. When each terminal unit is given individual address (self-address) or when various discrimination values (for example, a threshold for discriminating a fire, a threshold for discriminating a trouble, a threshold for testing an false alarm issue and miss alarm issue, accumulation time, timer set time and the like) are set, so-called dip switches are provided for the terminal units to perform the setting operation or the set values are previously stored in a mask ROM or an EPROM in the manufacturing process.
Since the conventional fire alarm system uses the dip switches, the mask ROM or the EPROM to set individual address for each terminal unit and a variety of discrimination values, use of the dip switch enables the address or the like to be changed easily at the spot at which the terminal unit is disposed after the terminal unit has been installed. However, there arises a problem in that the setting operation performed by using hexadecimal notation is too complicated and an error in setting to take place easily. What is worse, the set values can be changed by tampering or the set values can be disordered easily due to vibrations or the like.
Although use of the ROM or the EPROM enables the disorder of the set values due to vibrations to be prevented, the set values cannot be changed or an ultraviolet-ray eraser unit is required to erase the stored contents. Although the erase operation can be performed in the manufacturing process, the contents cannot be changed at the spot at which the terminal unit is installed. What is even worse, setting can be performed erroneously. If the address or the like is changed after the terminal unit has been installed, change to a new ROM or the like that has a new address is required. Thus, there arise problems in that complicated arranging and changing operations are required and that breakage of a pin of the ROM or the like and defective contact takes place on the situation.
In order to overcome the foregoing problems, a method has been suggested in which the address of the terminal unit is set from the fire receiver. The foregoing method has an arrangement that the terminal unit, the address of which is intended to be set, is called and a new address is transmitted to be set to the terminal unit.
In this case, the fire receiver calls the terminal unit, the address of which is intended to be changed, by using the present address and the new address is written on the called terminal unit. Although no problem takes place in a case where the new address is not used by another terminal unit, a plurality of terminal units having the same address are inevitably present if the same address as that of the other terminal unit is used. Therefore, there arises a risk that a plurality of terminal units simultaneously respond to a fire supervision. As a result, a problem arises in that the address cannot smoothly and accurately be set.
In a case where the method of the foregoing type is employed, a problem arises in that, if the address or the like is intended to be set to a new terminal unit having no set address, the fire receiver cannot call the terminal unit because the terminal unit has no address.
Since the method of the foregoing type, in which the address peculiar to each terminal unit is used to set the discrimination value, such as the address, is employed, a problem rises in that polling in a normal fire supervisory operation causes the terminal unit to erroneously perform an operation of setting the address or the like.